Of all the moons in the solar system, Iapetus is probably one of the strangest. The satellite of Saturn, named after the spear-wielding Titan, is only half the size of Earth's moon. But it holds numerous mysteries: It is indented at the poles and therefore more walnut-shaped than round. One side is dark, the other shines in bright white, and a mountain range stretches like a belt along its equator.

Even its orbit is strange: Iapetus is about three times as far from Saturn as its nearest neighbor, Titan. What's more, its orbit is inclined - so it moves up and down in its orbit instead of staying on the plane of Saturn's rings like the "normal" satellites.